You are absolutely correct - low battery charge. But, what caused it - generator going bad (doubtful) Old regulator suddenly brought back to life and not handling it too well after some use (probably), dirty contacts or older battery cables(most probably).

When you have a charging system that is this marginal in providing for the stock vehicle needs (ie the wrong engine oil could trip the tables on sufficient charge) it could be most anything.

On these systems, the battery acts as a peripheral - a pool if you will - to provide power to turn the starter and extra amps if the generator won't keep up. That's why if your battery is low in charge, it can't help the struggling generator keep the lights bright.

Angus' test is correct in theory, but checking voltage is an indicator of SYSTEM function, not COMPONENT function. IOW if you check voltage and it is in the range he specified, it says the charging system is on line. But it doesn't tell you if it is on line correctly or if not on line what is wrong.

The shop manual has a VERY simple test for checking generator output - in amps - which is the important factor, not voltage. I think I quoted it above toward the end of post #3. If the generator is putting out amps then the only problems you have if your battery is low, is the regulator, the shunt between the circuit breakers, dirty old connections, or bad battery.

The tests are pretty straight forward. If the generator test passes and all your connections and cables are good, I'd just replace the regulator at that point considering your battery is new.

The actual tests (non trouble shooting) start on page 249, and are pretty straight forward. If it gets to be too much write me a note at the real e-mail, and I'll recommend a summer grade of motor oil!